Sorry to double post, but this could be of use to folks here and in the FCP forum.

Just wanted to share this in case it happens to anyone else, it could save someone a big headache down the road...

I recently bought a new Canon 5DMIII and installed the updated EOS plugin for FCP to go along with it. When I pulled up Log and Transfer, none of the footage would transcode. Drag it to the bin, the wheels start turning etc but no new files are created. I wound up transcoding the footage in Magic Bullet Grinder since I already had that app, and I didn't have much footage to deal with so it was no biggie. But I had to know why this was happening.

Long story short, it was because I had the time code feature set to "free run". When I went in and changed it back to "record run", those clips would transcode fine. Even recording additional clips on the same card with the clips that were recorded in free run mode, as long as the individual clip was recorded in rec run mode, it transcodes just fine.

Anyway, avoid free run TC on the 5DM3 if you plan to transcode in FCP.
I'm shooting a week-long project next week... sure am glad I found this out before I shot all that!!

Record run mode is for generating time code only when the camera is recording. When recording stops, so does the TC clock. There was a time when it was helpful to have timecode that had no breaks in the numbers when editing was done on tape (some still use/need that). Record run gives you that. Consistent timecode regardless of the time in between takes.

Free run TC is a mode where the time code clock never stop regardless of whether the camera is recording or not.
Free run is primarily used for multi-camera setups. You'll sync all the cameras to one TC source set to free run mode. This way, any camera could cut at any time and start recording again and it will still be in sync with the other cameras. If you were using record run mode, you would be lost and completely out of sync with other cameras if you stopped recording.

Timecode is not really a big deal for most of us anymore. It is still critical for things that happen under the hood, but it's not something we have to give a lot of thought to anymore.

For me, I like using free run mode and set the TC to time of day. It can be a help when searching for footage. For example, if you are looking for a shot that happened around 3:00, finding that shot is a breeze. Just look for the footage that has TC numbers that begin around 15:00:00:00. And if you take any notes during the day, you simply write down the time of day next to your note and you'll be able to find your shot instantly.

Most DSLR cameras don't have timecode at all, this is another new feature of the 5DM3.
It brings it one more step towards being useful in more complex shooting/editing environments.
Not a big deal, but handy little helper tip that's nice to have if it's an option...

However, I'm having trouble with the EOS plugin recognizing the Mk3 footage at all. When I point Log and Transfer to the Mk3's folders, nothing comes up. I get a blank preview window and see none of the clips. The Mk2 folders work right away. I've confirmed that my camera setting is on record run.

There is an updated plugin on Canon's website so make sure that is up to date and you should be good to go. I use FCP7 as well and no (other) issues here. Just finished cutting a music video that I shot on Sunday and footage looks amazing! Loving this camera!